550 



ANTENNAS AND RF COMPONENTS 



The uses of 3-db hybrid junctions are many in radar systems, ^^ from their 

 use as a 3-db directional coupler and for power splitting, to deriving "sum" 

 and "difference" signals in the microwave bridge circuits of monopulse 

 antenna feeds. The use of 3-db hybrids in balanced mixers and duplexers 

 will be described later. 



Many other multiport hybrid junctions have been developed or devised 

 for special application. Among these are two of particular interest for 

 circularly polarized systems: the turnstile waveguide junction^^'^^ and the 

 trimode turnstile waveguide junction." The latter junction, shown 

 schematically in Fig. 10-23, has particular utility in a compact dual balanced 

 mixer for circularly polarized applications.^^ 



S^ 





Fig. 10-22 The Hughes H-Plane Folded Fig. 10-23 The Trimode Turnstile June- 

 Hybrid Tee, a 3-db Hybrid Junction. tion, a Symmetrical Seven-Port Hybrid 

 (Microwave Development Laboratories, Junction. 

 Inc.) 



The Mixer. The purpose of the mixer^^ in a radar receiver is to 

 convert the incoming microwave signal to an intermediate frequency (IF) 

 signal of similar character which can be amplified using low-frequency 

 techniques. This process is accomplished by mixing the received signal 



^''J. W. Sutherland, "Waveguide Hybrid Circuits and Their Use in Radar Systems," Etec- 

 tronic Eng. 28, 464-469 (1956). 



3'^M. A. Meyer and H. B. Goldbers;, "Applications of the Turnstile Junction," IRE Trans. 

 MTT-3, No. 6, 40-45 (December 1955). 



^^R. S. Potter and A. Sagar, "A New Property of the Turnstile Waveguide Junction," 

 1957 Proc. Natl. Electronics ConJ. 1.1, 452-458 (1958). 



s^R. S. Potter, "A Trimode Turnstile Waveguide Junction," IRE Convention Record 4, 

 Part 5, 36-43 (1956). 



^P. J. Allen and R. D. Tompkins, "An Instantaneous Microwave Polarimeter," Pf-oc. IRE 

 47, 1231-1237 (1959). 



39R. V. Pound, Microwave Mixers, McGraw-Hill Book Co., Inc., New York, 1948. 



